Present methods for the removal of polymeric substrates from surfaces such as aircraft, railcars and aging steel structures such as bridges (which may include lead based paint), involve the use of abrasives, highly alkaline compositions or materials which exhibit a high degree of toxicity and corrosiveness.
Typically, the method of choice is to sand blast the structure at high pressure. The process, however, produces airborne particulates, sometimes containing lead and silicates. Additionally, sand blasting expands exponentially the mass of contaminant to be treated or disposed.
Alternatives to the use of sand blasting include the chemical strippers, which generally fall into one of two categories. Some strippers fall into both. One category is the caustic removers, the other is solvent based removers. The caustic removers may be formulated as liquids or paste compositions.
Stripping compositions containing strong corrosive agents, for example, phenol, in combination with methylene chloride and other substances are presently in use for stripping commercial aircraft. When applied, these compositions cause the paint to swell and loosen from the grounding. The outer coating is then scraped off by hand. This rather tedious procedure has several drawbacks. First, the solvents used (in particular, phenol and methylene chloride) are highly toxic, caustic, deleterious and/or carcinogenic. Second, safety regulations require workers to wear protective clothing and gas masks, both of which must be disposed of after only a single use. A third drawback is that the flooring under the airplane must be fully covered to protect it from drippings and penetration by the corresive agents. Fourth, the paint residue (which may amount to several tons of waste material from a single aircraft), clothing and floor covering must be specially disposed of as a toxic waste at great expense.